In a vehicle such as an electric vehicle that is spreading widely, batteries are installed as a supply source of electric power for a traveling motor. The batteries are housed in a case as a battery unit. The battery unit is installed in the vehicle body. In such an electric vehicle, in a case where electric power stored in the battery unit installed in the vehicle body is discharged, it is necessary to charge the battery unit, or replace the discharged battery unit with a charged battery unit. The type of the electric vehicle requiring the replacement of the battery unit includes an electric vehicle enabling the installation of a battery unit on the bottom part of a vehicle body and enabling replacement of the battery unit from below the vehicle body by using a battery unit installation apparatus. In such a battery unit replacement method, various vehicle battery unit installation apparatuses are proposed in order to install the battery unit in the vehicle body efficiently.
For example, a vehicle battery unit installation apparatus disclosed in Patent Document 1 includes a bolt, provided to vertically extend on the lower part of a vehicle body, and a nut secured to the bolt. In the vehicle battery unit installation apparatus, a battery unit can be installed in the lower part of the vehicle body by using the bolt and the nut.